To see the tip clearance effect on a centrifugal compressor, time-resolved flow measurements were carried out at the discharge of a centrifugal compressor impeller, which is 30 deg back swept from radial and operated at the blade tip speed of 260 m/s. Tested were six cases of tip clearance ratio ranged from 0.06 to 0.21. A fast response aerodynamic probe equipped with a single pressure sensor was used for the flow measurements. From the distribution of time-resolved relative velocity, the jet-wake structure was observed. The wake downstream of the splitter blade was located in the shroud-suction corner, but that downstream of the full blade was in the mid-shroud. By increasing the tip clearance, the wake region was increased and the deficit of the relative total pressure governed the wake region, therefore, the loss was enlarged.

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